Heretofore, a punch apparatus has been known for punching a hole in a workpiece by pushing a punch with respect to the workpiece in the form of a sheet.
In this type of punch apparatus, for example, as disclosed in U.S. Pat. No. 6,450,082, a sector-shaped cylinder chamber is formed in the interior of a body having two ports, a piston, which is tiltable about an upper end portion thereof serving as a supporting point, is disposed in the interior of the chamber, and a rod is connected through a link, which is supported substantially in a center portion of the piston. One end of the link is supported rotatably on the piston via a pin, and similarly, another end of the link is supported rotatably with respect to the upper end of the rod via a pin. Further, the rod is supported displaceably in a vertical direction in the interior of the body, and on the lower end of the rod, a punch is mounted, which is used when machining is performed on the workpiece.
In addition, a pressure fluid is supplied to one of the ports to thereby cause the other end side of the piston to be tilted upwardly about the one end portion thereof, and in this state a workpiece is set, whereupon the supply of pressure fluid is switched to the other port. Accordingly, the piston is pushed by the pressure fluid supplied into the cylinder chamber, and the other end side of the piston is tilted downward, accompanied by the rod being pushed downwardly through the link, so that a hole-punching process or the like is performed on the workpiece. At this time, by way of a toggle mechanism, which is made up from the link disposed between the piston and the rod, the displacement force of the piston is boosted through the link, and the boosted force is transmitted to the rod.